Medical Aspects of the Persistent Vegetative State

Prognosis for Recovery

There are two dimensions of recovery from a persistent vegetative state: recovery of consciousness and recovery of function. Recovery of consciousness can be verified by reliable evidence of awareness of self and the environment, consistent voluntary behavioral responses to visual and auditory stimuli, and interaction with others. Recovery of function is characterized by communication, the ability to learn and to perform adaptive tasks, mobility, self-care, and participation in recreational or vocational activities. Recovery of consciousness may occur without functional recovery, but functional recovery cannot occur without recovery of consciousness. In some instances, during the early stages of recovery of consciousness, external manifestations may not be immediately apparent. Repeated examinations over time are necessary to ensure the consistency and accuracy of signs of recovery.

The prognosis for cognitive and functional recovery depends on the cause of the underlying brain disease. The Glasgow Outcome Scale classifies outcome in five categories: good recovery, moderate disability, severe disability, persistent vegetative state, and death108. Patients with a good recovery have the capacity to resume normal occupational and social activities, although there may be minor physical or mental deficits or symptoms. Patients with moderate disability are independent and can resume almost all activities of daily living. They are disabled to the extent that they can no longer participate in a variety of social and work activities. Patients with severe disability are no longer capable of engaging in most previous personal, social, and work activities. Such patients have limited communication skills and abnormal behavioral and emotional responses. They are partially or totally dependent on assistance from others in performing the activities of daily living.

ACUTE TRAUMATIC AND NONTRAUMATIC INJURIES

Figure 1.Outcome for Patients in a Persistent Vegetative State (PVS) after a Traumatic or Nontraumatic Injury.Table 3.Incidence of Recovery of Consciousness and Function in Adults and Children in a Persistent Vegetative State (PVS) after Traumatic or Nontraumatic Brain Injury.Table 4.Probability of Recovery of Consciousness and Function at 12 Months in Adults and Children in a Persistent Vegetative State (PVS) Three or Six Months after Traumatic or Nontraumatic Injury.

Recovery of consciousness after 12 months is unlikely in adults and children who have had traumatic injuries. Recovery of consciousness after three months is rare in adults and children with nontraumatic injuries (Figure 1 and Table 3 and Table 4).

Traumatic Injuries in Adults

For patients in a vegetative state as a result of traumatic brain injury, the prognosis for recovery remains unfavorable. Recovery of consciousness and function was determined by reviewing data from previously described series of patients rather than individual case reports. Data were available on 434 patients in a vegetative state one month after a severe head injury (Figure 1 and Table 3)47,49,50,106,109,110 (and Tillet JA: personal communication). Recovery of consciousness varied with time. Three months after injury, 33 percent of the patients had recovered consciousness; 67 percent had died or remained in a vegetative state. Recovery had occurred in 46 percent of the patients at 6 months and in 52 percent at 12 months. Recovery after 12 months was reported in only 7 of the 434 patients47,49. One patient recovered consciousness 30 months after injury and remained severely disabled47, 111. The Traumatic Coma Data Bank study reported that 6 of 93 adult patients in a vegetative state recovered consciousness one to three years after injury49. Four of these six patients had severe disability, and one had moderate disability; the status of the sixth patient could not be determined. Five of the six patients were under 30 years of age. There have been no other well-documented reports of recovery of consciousness in patients in a persistent vegetative state more than 12 months after a traumatic injury.

Good recovery of function is also unlikely. Among the 434 patients in a vegetative state, the outcome at one year, according to the Glasgow Outcome Scale, was as follows: 33 percent had died, 15 percent were in a persistent vegetative state, 28 percent had severe disability, 17 percent had moderate disability, and 7 percent had a good recovery. Of the 7 percent of patients who had a good recovery, over half showed signs of improvement within three months after injury, and almost all within six months after injury. For the entire group of 434 patients, the incidence of a good recovery beginning 6 to 12 months after injury was less than 0.5 percent. No patient had a good recovery that began after 12 months. Among patients who recovered with moderate or severe disability, almost all showed signs of improvement within six months after injury. A later recovery was almost invariably associated with severe disability.

Age is an important factor affecting outcome. Among patients who have had traumatic injuries, those over the age of 40 years have a smaller chance of improvement than those who are younger; recovery without severe disability is rare, especially after three months47. Ventilatory dysfunction, lack of early motor reactivity, late-onset epilepsy, or the development of hydrocephalus may also indicate a poorer prognosis for recovery of awareness55, 112.

Nontraumatic Injuries in Adults

Adults in a coma immediately after a nontraumatic injury have a poorer prognosis than those in a coma after a traumatic injury, with 85 percent or more dying within the first month after the insult or remaining in a vegetative state52,56. Later recovery of consciousness and function was determined by reviewing data from previously described series consisting of 169 patients who were in a vegetative state one month after a nontraumatic injury (Figure 1 and Table 3)37,42,43,51. Recovery of consciousness after a nontraumatic injury is unlikely. Of the 169 patients with such injuries, only 11 percent had recovered consciousness three months after injury; 89 percent remained in a vegetative state or had died (Figure 1 and Table 3). Six months after injury, only two additional patients had recovered consciousness. One year after injury, 15 percent of the 169 patients had recovered consciousness, 32 percent were in a persistent vegetative state, and 53 percent had died.

Table 5.Verified Reports of Five Patients with a Late Recovery from a Persistent Vegetative State (PVS).

Recovery of function in the 15 percent of patients who regained consciousness was extremely poor. Only one patient had a good recovery. Two additional reports of individual patients with good functional recovery after nontraumatic injury have been published. In both patients, improvement began within two months after a hypoxic injury78,113. There have been reports of five other patients who began to recover from a vegetative state more than six months after a nontraumatic injury. Two had moderate disability, and three had severe disability (Table 5).

Traumatic Injuries in Children

Recovery of consciousness and function in children after a traumatic injury was determined by reviewing data on 106 patients in previously reported series (Figure 1 and Table 3)49, 110,117-119 (and Tillet JA: personal communication). The prognosis for recovery of consciousness after a traumatic injury is slightly better in children than in adults (Figure 1). Of the 106 children in a vegetative state one month after a severe head injury, 24 percent had regained consciousness within three months. At one year, only 29 percent remained in a vegetative state, 9 percent had died, and 62 percent had recovered consciousness. None of the children recovered consciousness after 12 months.

Recovery of function was comparable to that in the adults. At one year, 35 percent of the children had severe disability, 16 percent had moderate disability, and 11 percent had made a good recovery. As in adults, if recovery of consciousness from the post-traumatic vegetative state began before six months, a higher functional grade of recovery was likely118. However, some children had a good recovery at six months or had only moderate disability at one year, whereas in adults recovery after six months was usually associated with severe disability.

Nontraumatic Injuries in Children

The prognosis for recovery after nontraumatic injuries in children appears to be similar to the prognosis for adults. However, the available data are limited, since previously described series total only 45 patients (Figure 1 and Table 3)44,66.86. Recovery of consciousness in children, as in adults, was primarily observed within the first three months after injury. By that time, 11 percent of the patients had regained consciousness; by one year, only an additional 2 percent had recovered consciousness. At one year, the majority of the children remained in a vegetative state (65 percent) or had died (22 percent). Apparent recovery of consciousness after one year has been reported in several children in a vegetative state after a hypoxic-ischemic injury119. However, these children recovered a level of function described as socially responsive, meaning that they smiled in response to the presence of other people but without other evidence of awareness. The prognosis for recovery from a vegetative state in young infants with birth injuries and perinatal asphyxia is more variable than in older infants and children3,4,58,66.

The prognosis for recovery of function in children with a nontraumatic injury is somewhat better than that for adults. Of the 13 percent of children who recovered consciousness, 6 percent had a good recovery, and the other 7 percent had severe disability; there were no reports of moderate disability.

DEGENERATIVE AND METABOLIC DISEASES

Patients in a vegetative state due to degenerative or metabolic diseases have no possibility of recovery. Some patients may temporarily lapse into a vegetative state when systemic illness causes a reversible depression of neurologic function. This possibility must be considered before determining that a patient's vegetative state is irreversible.

DEVELOPMENTAL MALFORMATIONS

Infants and children with brain malformations severe enough to cause a developmental vegetative state are unlikely to become conscious; those who do are in most cases severely disabled. Anencephaly is the only malformation for which it is clear at birth that there is no possibility of recovery of consciousness. The complete absence of the cerebral cortex in anencephalic infants precludes consciousness20.

Other malformations diagnosed at birth may result in a vegetative state. If the patient remains in a vegetative state at three months of age, the prognosis for any improvement is quite poor10,66. Lack of evidence of consciousness in such infants by the age of six months almost completely precludes the potential for future improvement.

VERIFIED AND UNVERIFIED LATE RECOVERY

Few patients in a persistent vegetative state have undergone a verified recovery of consciousness more than 12 months after a traumatic injury or more than 3 months after a nontraumatic injury (Table 5). One patient recovered 30 months after a traumatic brain injury; four patients recovered 8 to 22 months after a hypoxic-ischemic or cerebrovascular injury. An additional six patients, described in the study by the Traumatic Coma Data Bank, were reported to have recovered consciousness beginning one to three years after injury. Further investigation of these six patients suggests that only half recovered awareness after one year; one was moderately disabled, and the others had severe disabilities49. Two recent studies in adults and children have also reported that a few patients with traumatic and nontraumatic injuries recovered consciousness after the expected intervals119,120. The task force knows of no other cases of verified late recovery.

Several reports in the popular media have described dramatic recovery from a persistent vegetative state. In most reports, recovery of consciousness and function occurred within the time frames noted above121. Unusual cases in the medical literature or popular media are poorly documented, the nature of the patients' neurologic condition is unclear, or the timing of the entry into the vegetative state is extremely atypical114,122. A tabular summary of these cases is available from the task force. Several of these reports have been investigated by members of the task force, and it appears likely that, although the patients were not directly examined, a late recovery of consciousness did occur. The total number of such patients is extremely small, however, considering the estimated prevalence of the persistent vegetative state, and all were apparently left with severe disability.

PROBABILITY OF RECOVERY

On the basis of the data in the series noted above, we have estimated the probability of recovery of consciousness in adults and children who were in a vegetative state one month after an acute traumatic or nontraumatic injury (Table 4). The outcome probability at 12 months was determined in patients who remained in a vegetative state at 3 months and at 6 months. In addition, the probability of functional recovery was determined for two possible outcomes: good recovery or recovery with moderate disability, and recovery with severe disability. On the basis of these probabilities, a persistent vegetative state can be judged to be permanent 12 months after a traumatic injury in adults and children; recovery after this time is exceedingly rare and almost always involves a severe disability. In adults and children with nontraumatic injuries, a persistent vegetative state can be considered to be permanent after three months; recovery does occur, but it is rare and at best associated with moderate or severe disability.